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Exercise Physiology MPB 326

Exercise Physiology MPB 326. David Wasserman, PhD Light Hall Rm 823 3-7336. The Remarkable Thing about Exercise. The Great Debate. Top-down Feedback control. Energy Metabolism and the Three Principles of Fuel Utilization.

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Exercise Physiology MPB 326

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  1. Exercise PhysiologyMPB 326 David Wasserman, PhD Light Hall Rm 823 3-7336

  2. The Remarkable Thing about Exercise

  3. The Great Debate • Top-down • Feedback control

  4. Energy Metabolism and the Three Principles of Fuel Utilization

  5. The need for energy starts when calcium is released from the sarcoplasmic reticulum of contracting muscle

  6. The Working Muscle

  7. Energy for Contraction

  8. Muscle relaxation requires energy too!

  9. Where does this ATP come from?

  10. Sources of ATP Stored in muscle cell (limited) Synthesized from macronutrients Common Processes for ATP production Anaerobic System a. ATP-PC (Phosphagen system) b. Anaerobic glycolysis (lactic acid system) Aerobic System a. Aerobic glycolysis b. Fatty acid oxidation c. TCA Cycle

  11. ATP-PCr (Phosphagen system) Stored in the muscle cells (PCr > ATP) ATP + H2O  ADP + Pi + E (ATPase hydrolysis) PCr + ADP  ATP + Cr (creatine kinase reaction) ADP + ADP  ATP + AMP (adenylate kinase) PCr represents the most rapidly available source of ATP a) Does not depend on long series of reactions b) No O2 transportation required c) Limited storage, readily depleted ~ 10 s

  12. Glycolysis Glucose + 2 ADP + 2 Pi + 2 NAD+ 2 Pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O

  13. Lactate Dehydrogenase Hypoxic conditions Pyruvate + CoA + NADH + H+ Lactate + NAD+

  14. Pyruvate Dehydrogenase Lots of Oxygen Pyruvate + CoA + NADP+ Acetyl-CoA + CO2 + NADPH

  15. Pyruvate Dehydrogenase Pyruvate + CoA + NADP+ Acetyl-CoA + CO2 + NADPH

  16. TCA Cycle Acetyl-CoA + 3 NAD+ + FAD + GDP + Pi + 2H20 CoASH + 3 NADH + 3H+ + FADH2 + GTP + 2CO2

  17. Beta Oxidation of Fatty Acids 7 FAD + 7 NAD+ + 7 CoASH + 7 H2O + H(CH2CH2)7CH2CO-SCoA 8 CH3CO-SCoA + 7 FADH2 + 7 NADH + 7 H+

  18. Summary of ATP Production via Lipid Oxidation ATP Balance Sheet for Palmitic Acid (16 carbon) ATP • Activation of FA chain -1 • ß oxidation (16 Carbons / 2) –1 = 7 (at 5 ATP each) 35 • Acetyl-CoA (16 Carbons / 2) = 8 (at 12 ATP each) 96 Total per chain 130

  19. Electrochemical Energy and ATP Synthesis

  20. Energy for “Burst” and Endurance Activities • Rate of ATP Production (M of ATP/min) • phosphagen system ..............4 • anaerobic glycolysis..………2.5 • aerobic system.......................1 How long Can it Last? • phosphagen system...8 to 10 sec • anaerobic glycolysis…1.3 to 1.6 min • aerobic system.........unlimited time(as long as nutrients last)

  21. Aerobic Energy • During low intensity exercise, the majority of energy is provided aerobically • Energy produced aerobically requires O2 • Therefore, O2 uptake can be used as a measure for energy use

  22. Exercise Testing in Health and Disease

  23. I N C R E M E N T A L 4 VO2 (l/min) Severe 2 Heavy Moderate 0 150 300 Work Rate (Watts) Oxygen Uptake and Exercise Domains

  24. Heart Disease Onset of lactic acidosis Athlete Anaerobic Threshold Concept Exercise 15 Blood Lactate mM 10 5 0 150 50 100 200 250 Rest Period Exercise (watts)

  25. Bill Rodgers Anaerobic Threshold in Some Elite Long Distance Athletes can be close to Max Exercise 15 Onset of lactic acidosis Blood Lactate mM 10 5 0 60 20 40 Basal Oxygen Uptake 80 100 Oxygen Uptake (% maximum)

  26. Oxygen Deficit and Debt

  27. Oxygen Uptake and Exercise Domains C O N S T A N T L O A D Severe 4 Heavy 2 Moderate 0 12 24 Time (minutes)

  28. Lactate and Exercise 12 Blood Lactate mM 6 0 12 24 0 Time (minutes)

  29. Three Principles of Fuel Utilization during Exercise • Maintaining glucose homeostasis • Using the fuel that is most efficient Storage Metabolic • Preserving muscle glycogen core

  30. Glucose homeostasis is usually maintained despite increased glucose uptake by the working muscle Moderate Exercise 1 0 0 8 0 Blood 6 0 Glucose ( mg / dl ) 4 0 2 0 0 5 4 R a t e s o f G l u c o s e E n t r y a n d E n t r y 3 R e m o v a l f r o m t h e B l o o d 2 R e m o v a l - 1 - 1 ( m g • k g • m i n ) 1 0 - 3 0 0 3 0 6 0 T i m e ( m i n )

  31. Carbohydrate Stores after an Overnight FastSedentary 100 grams Liver Glycogen Blood Glucose Muscle Glycogen 400 grams 4 grams

  32. Carbohydrate Stores after an Overnight Fast 1 hr of Exercise Liver Glycogen Blood Glucose Muscle Glycogen 400 grams 4 grams 100 grams

  33. Carbohydrate Stores after an Overnight Fast 2 hr of Exercise Liver Glycogen Blood Glucose Muscle Glycogen 400 grams 4 grams 100 grams

  34. Carbohydrate Stores after an Overnight Fast 3 hr of Exercise Liver Glycogen Blood Glucose Muscle Glycogen 400 grams 4 grams 100 grams

  35. Carbohydrate Stores after an Overnight Fast 4 hr of Exercise Liver Glycogen Blood Glucose Muscle Glycogen 400 grams 4 grams 100 grams !!!

  36. Contribution of different fuels to metabolism by the working muscle is determined by 3 objectives: • Maintaining glucose homeostasis • Using the fuel that is most efficient Storage Metabolic • Preserving muscle glycogen core

  37. The Most Efficient Fuel depends on Exercise Intensity and Duration Metabolic Efficiency CHO is preferred during high intensity exercise because its metabolism yields more energy per liter of O2than fatmetabolism. kcal/l of O2 CHO 5.05 Fat 4.74 CHO can also produce energy without O2!!! Storage Efficiency Fat is preferred during prolonged exercise because its metabolism provides more energy per unit mass than CHO metabolism. kcal/g of fuel CHO 4.10 Fat 9.45 Fats are stored in the absence of H2O.

  38. Effects of Exercise Intensity • Plasma FFA (fat from fat cells) is the primary fuel source for low intensity exercise • As intensity increases, the source shifts to muscle glycogen From: Powers & Howley. (2007). Exercise Physiology. McGraw-Hill.

  39. Effects of Exercise Duration From: Powers & Howley. (2007). Exercise Physiology. McGraw-Hill.

  40. Fuel Selection • As intensity increases carbohydrate use increases, fat use decreases • As duration increase, fat use increases, carb use decreases From: Powers & Howley. (2007). Exercise Physiology. McGraw-Hill.

  41. Contribution of different fuels to metabolism by the working muscle is determined by 3 objectives: • Maintaining glucose homeostasis • Using the fuel that is most efficient Storage Metabolic • Preserving muscle glycogen core

  42. Other fuels are utilized to spare muscle glycogen during prolonged exercise thereby delaying exhaustion Adipose Lactate NEFA Pyruvate Glycerol Amino Acids Muscle NEFA GLY ATP GNG GLY Glucose Liver As exercise duration increases: • More energy is derived from fats and less from glycogen. • Amino acid, glycerol, lactate and pyruvate carbons are recycled into glucose.

  43. Contribution of different fuels to metabolism by the working muscle is determined by 3 objectives: • Maintaining glucose homeostasis • Using the fuel that is most efficient Storage Metabolic • Preserving muscle glycogen core

  44. Discussion Question Can you accommodate all three principles of fuel utilization? Why not? What is the Consequence?

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